Influence of particle properties on iron flocculation

Influence of particle properties on iron flocculation

de Ridder, D.J. (TU Delft Sanitary Engineering)
van Halem, D. (TU Delft Sanitary Engineering)

2018-10-01

In this study, the importance of charge interactions during flocculation of Fe³⁺ in the presence of particles and anions/cations at various pH values was investigated. SiO_{2, (s)} and ZnO_(s) were dosed as particles to promote charge interactions and/or serve as a nucleus to accelerate floc formation. In the pH range 6–9, SiO_{2, (s)} is negatively charged, while ZnO_(s) carries a positive charge. Ca²⁺ and HPO₄ ^2- were selected to investigate charge interactions in the water phase. A significant delay in floc growth due to charge repulsion between negatively charged iron species was observed at pH_ini 9. For positively charged species at pH_ini 6, a delay in floc growth was observed as well, but to a lesser degree. These effects could be neutralized by either dosing (positively charged) ZnO_(s) or Ca²⁺ at pH_ini 9, or (negatively charged) SiO_{2, (s)} at pH_ini 6. The addition of phosphate did not hinder floc growth at pH_ini 6. While phosphate completely inhibited floc growth at pH_ini 7–9 in the presence of negatively charged SiO_2, (s), the presence of positively charged ZnO_(s) partly neutralized the detrimental influence of phosphate on floc growth. Similarly, dosing Ca²⁺ partly neutralized the effect of phosphate.

Charge interaction
Iron flocculation
Particles

http://resolver.tudelft.nl/uuid:8d4414d0-a7a2-4ccb-ab88-826a0bef2a3a

https://doi.org/10.2166/ws.2017.216

2019-10-01

1606-9749

Water Science and Technology: Water Supply, 18 (5), 1617-1624

Institutional Repository

journal article

© 2018 D.J. de Ridder, D. van Halem